ACQUISITIONS (Grand River Gathering) (Details) (USD $)
12 Months Ended 0 Months Ended 0 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Oct. 27, 2011
Grand River Gathering, LLC
hp
mi
Dec. 31, 2011
Grand River Gathering, LLC
Oct. 27, 2011
Minimum
Grand River Gathering, LLC
Oct. 27, 2011
Maximum
Grand River Gathering, LLC
Oct. 27, 2011
Weighted Average
Grand River Gathering, LLC
Oct. 27, 2011
Sponsors
Grand River Gathering, LLC
Oct. 27, 2011
Gas gathering agreement contract intangibles
Grand River Gathering, LLC
Oct. 27, 2011
Rights-of-way
Grand River Gathering, LLC
Jun. 30, 2012
Purchase Price Allocation Adjustments
Grand River Gathering, LLC
Jun. 30, 2012
Construction in progress
Purchase Price Allocation Adjustments
Grand River Gathering, LLC
Business Acquisition [Line Items]                          
Useful lives           10 years 25 years 12 years 9 months          
Length of pipeline acquired (in miles)       260                  
Capacity of compression facilities acquired (in horsepower)       90,000                  
Equity contribution $ 0 $ 0 $ 425,000,000 $ 410,000,000                  
Proceeds from promissory notes                 200,000,000        
Nonrecurring transaction costs         3,200,000                
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]                          
Purchase price       590,210,000                  
Property, plant, and equipment       295,240,000                 (4,700,000)
Intangible assets                   244,100,000 8,016,000 (37,900,000)  
Total assets acquired       547,356,000                  
Deferred revenue       1,770,000                  
Other current liabilities       854,000                  
Total liabilities assumed       2,624,000                  
Net identifiable assets acquired       544,732,000                  
Goodwill $ 115,888,000 $ 45,478,000 $ 45,478,000 $ 45,478,000 $ 45,500,000